1. **Problem Statement:**
Sketch and analyze the curves for the following polynomial functions:
a) $y = x^2 (x + 2)$
b) $y = x^2 (5 - 2x)$
c) $y = (x + 1)^2 (x - 2)$
d) $y = (x - 2)^2 (10 - 3x)$
2. **General Approach:**
For each polynomial, we will:
- Identify the degree and leading term.
- Find the roots (x-intercepts) by setting $y=0$.
- Determine the multiplicity of each root to understand the behavior at intercepts.
- Analyze end behavior based on the leading term.
- Sketch the curve accordingly.
3. **Detailed Steps:**
### a) $y = x^2 (x + 2)$
- Expand: $y = x^3 + 2x^2$
- Degree: 3 (cubic), leading term $x^3$ (positive leading coefficient)
- Roots: $x=0$ (multiplicity 2), $x=-2$ (multiplicity 1)
- Behavior at $x=0$: touches x-axis and turns (because multiplicity 2)
- Behavior at $x=-2$: crosses x-axis (multiplicity 1)
- End behavior: as $x \to \infty$, $y \to \infty$; as $x \to -\infty$, $y \to -\infty$
### b) $y = x^2 (5 - 2x)$
- Expand: $y = 5x^2 - 2x^3$
- Degree: 3, leading term $-2x^3$ (negative leading coefficient)
- Roots: $x=0$ (multiplicity 2), $x=\frac{5}{2}$ (multiplicity 1)
- Behavior at $x=0$: touches and turns
- Behavior at $x=\frac{5}{2}$: crosses
- End behavior: as $x \to \infty$, $y \to -\infty$; as $x \to -\infty$, $y \to \infty$
### c) $y = (x + 1)^2 (x - 2)$
- Expand: $y = (x^2 + 2x + 1)(x - 2) = x^3 - 2x^2 + 2x^2 - 4x + x - 2 = x^3 - x - 2$
- Roots: $x = -1$ (multiplicity 2), $x=2$ (multiplicity 1)
- Behavior at $x=-1$: touches and turns
- Behavior at $x=2$: crosses
- End behavior: as $x \to \infty$, $y \to \infty$; as $x \to -\infty$, $y \to -\infty$
### d) $y = (x - 2)^2 (10 - 3x)$
- Expand: $y = (x^2 - 4x + 4)(10 - 3x) = 10x^2 - 40x + 40 - 3x^3 + 12x^2 - 12x = -3x^3 + 22x^2 - 52x + 40$
- Roots: $x=2$ (multiplicity 2), $x=\frac{10}{3} \approx 3.33$ (multiplicity 1)
- Behavior at $x=2$: touches and turns
- Behavior at $x=\frac{10}{3}$: crosses
- End behavior: as $x \to \infty$, $y \to -\infty$; as $x \to -\infty$, $y \to \infty$
4. **Summary:**
- Multiplicity 2 roots cause the graph to touch and turn at the x-axis.
- Multiplicity 1 roots cause the graph to cross the x-axis.
- Leading term determines end behavior.
This analysis helps sketch each curve accurately.
Polynomial Curves 198E50
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